Effect of River Discharge On Fish Recruitment in the Apalachicola River, FL

Increased water demands during recent years and historic impacts from maintaining a commercial navigation channel by the US Army Corps of Engineers within the Apalachicola-Chattahoochee-Flint River watershed has resulted in conflicts among water users from Alabama, Florida and Georgia. The Apalachicola River has experienced a decline in the frequency, magnitude and duration of spring floodplain inundation compared to historical trends.  In order to explore effects of river discharge level on fishes in the Apalachicola River, FL, from 2003-2012 we conducted annual standardized boat electrofishing samples in the main channel and slough habitats to investigate fish recruitment and population dynamics in response to river discharge.  We compared discharge to multiple age groups of three target species: redear sunfish Lepomis microlophus, largemouth bass Micropterus salmoides, and spotted sucker Minytrema melanops.  Age-0 catch rates for all three species indicated significant positive relationships to river discharge levels that maintained floodplain inundation during spring-summer. Further, strong year-classes remained abundant within the population through subsequent years.  Slough habitats are important and utilized by all three species, particularly juvenile redear sunfish and spotted suckers.  Our recent results suggest that reduced flows and floodplain flooding during spring-summer likely adversely affect fish recruitment.